Heat-seal failure prevention apparatus

ABSTRACT

A co-injected molded multi-layer article has inner and outer layers, an interior layer contained within the inner and outer layers and a surface portion to which a closure or other component may be heat-sealed. The article is molded by co-injecting the inner, outer and interior layer materials into a mold cavity of a mold. The interior layer material is caused to flow along a steam line offset from the zero velocity gradient of the combined material flow and biased toward a material flow for forming an outer wall of the multi-layer article. The resultant molded multi-layer article contains an interior layer located in a heat sealable region that avoids a breach or failure during a heat seal operation to seal an opening of the molded article.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation under 35 U.S.C. §120 of U.S. patentapplication Ser. No. 13/303,758, filed Nov. 23, 2011, which claimsbenefit under 35 U.S.C. §119(e) of U.S. Provisional Patent ApplicationNo. 61/416,903 filed Nov. 24, 2010, both of which are incorporated byreference herein in their entirety.

FIELD OF THE INVENTION

The present invention relates to multi-layer injection molded articles.In particular, embodiments relate to multi-layer molded plastic articlessuitable for sealing with a heat sealing mechanism without damaging abarrier or scavenger component embedded in the article.

BACKGROUND

Injection molded articles are used for a variety of purposes. Plasticinjection molded articles are commonly made from materials such asPolyethylene Terephtholate (PET) or Polypropylene (PP). In manyapplications, an injection-molded container has a lid or closureheat-sealed to an open portion of the container. Often, the containerhas a flange, lip or other protuberance at the open end of the containeragainst which the closure is sealed. Commonly, the closure comprises afirst layer configured to enclose the container and a plastic layercoating at least a portion of the first layer that contacts thecontainer. In many applications, the first layer contains a foil, e.g.,aluminum foil, or another material that provides a gas and/or waterbarrier for the container opening. The plastic layer is typically thesame (or similar) material as the container that is capable of forming aheat-seal with the container material. The plastic material of thecontainer and the closure in the area where the container and plasticlayer contact is then heated (by various known heating methods), oftenwith compression, which sufficiently softens and/or melts the plasticlayer and/or adjacent plastic container material to seal the lid to thecontainer. The heat-seal process results in a heat-affected zone in thecontainer material adjacent to the heat-seal, e.g., about 10% of thethickness of the flange.

Plastic materials such as PET and PP are gas (e.g., oxygen, nitrogen,etc.) permeable. For applications in which gas permeability isundesirable, for example, food products, medicines and products thatdegrade upon gaseous exposure, a barrier material or scavenger materialis co-injected with the plastic material. Typically, the barriermaterial, such as Ethyl Vinyl Alcohol (EVOH), is injected at theinterior of the PET or PP material stream, forming an EVOH interiorlayer embedded within an inner and outer layer of PET or PP.

This co-injection process has previously been limited to articles thatare essentially symmetrical in shape due to process limitations withrespect to forming the barrier layer. In addition, in order to providean interior layer that sufficiently extends through the molded articleto prevent undesirable gas permeation, the interior layer material isinjected into the mold in such a manner so that it flows throughoutessentially the entire mold.

However, injecting the interior layer material in this manner can causethe interior layer material to flow beyond the desired interiorlocation. For example, the interior layer material can penetrate orbreakthrough the flow front or leading edge of the inner and outer layermaterial. If the interior layer penetrates into the heat-affected zoneof the heat-seal, delamination can occur, leading to heat-seal failure.Presently known solutions attempt to more precisely control the flow ofthe interior layer material, e.g., by controlling injection pressure,temperature, timing, injection location, etc., so that the interiorlayer flows sufficiently throughout the mold cavity without flowingbeyond the desired interior layer locations. Nonetheless, remainingsystemic and process variations still result in interior layer materialflowing into the heat-affected zone.

Accordingly, there is a need for methods and apparatuses for forminginjection molding articles having an interior layer where the interiorlayer material does not detrimentally extend or impinge into theheat-seal affected zone. There is further a need for co-injection moldedarticles containing such an interior layer, but in which the interiorlayer material does not detrimentally extend or impinge into theheat-seal affected zone.

SUMMARY OF THE INVENTION

Exemplary methods and systems are taught herein to form a multi-layermolded article with an embedded barrier layer or scavenger layer thatremains intact and functional after a heat seal process to seal anopening in the multi-layer molded article. Exemplary multi-layer moldedarticles with an embedded barrier layer or scavenger layer that remainintact and functional after a heat seal process to seal an opening inthe multi-layer molded article are taught herein. In some exemplaryembodiments the heat sealable zone of the exemplary multi-layer moldedarticles is located in a rim or flange portion extendingcircumferentially about an open end of the multi-layer molded articles.

In some embodiments, exemplary co-injection molding apparatuses includea mold that defines a mold cavity for co-injection/extrusion forming amulti-layer molded article having an inner layer, an outer layer and aninterior layer embedded within the inner and outer layers (i.e., skin)and a surface in a heat-sealable portion to which a closure or othercomponent may be heat-sealed thereto. The interior layer may be a firstpolymeric material. The inner and outer layers may be a second polymericmaterial. The interior layer may be substantially gas-impermeablerelative to the permeability of the second polymeric material. Theinterior layer may be substantially gas-scavengable relative to thepermeability of the second polymeric material. The molding apparatus isconfigured to simultaneously inject the inner layer polymeric material,the outer layer polymeric material and the interior layer polymericmaterial into the mold cavity to form the resulting multi-layered moldedarticle. The molding apparatus is further configured to inject theinterior layer polymeric material into the mold cavity along a flow lineoffset from the zero velocity gradient(s) of the combined material flow.The combined material flow is formed from the inner polymeric materialflow, the interior polymeric material flow and the outer polymericmaterial flow. The molding apparatus is further configured to inject theinterior polymeric material to the side of the zero velocity gradientthat is opposite or away from the heat-sealable surface portion. Duringthe heat sealing operation up to 10% or more of the thickness of theheat sealable portion of the multi-layered molded article melts, yet theinterior polymeric material remains intact and functional as a barrierlayer or a scavenger layer in the multi-layered molded article.

In other embodiments, exemplary methods for forming a multi-layer moldedarticle with a heat sealable zone are taught. The exemplary methodsinject the interior layer polymeric material to the side of the zerovelocity gradient of a combined material flow that is opposite or awayfrom the heat-seal surface of a heat-sealable portion of the resultingmulti-layer molded article. The interior layer polymeric material formsa barrier layer or a scavenger layer in the resulting multi-layer moldedarticle. The barrier layer or the scavenger layer is embedded in a skinformed from the inner and outer polymeric material. The exemplarymethods form the resulting multi-layer molded article with a heatsealable portion to which a closure or other component may beheat-sealed. The exemplary methods direct a leading edge of the interiorpolymeric material into the heat sealable portion and subsequentlyposition the leading edge of the interior polymeric material in the heatsealable portion to avoid failure of the inner layer in the sealableportion during a heat sealing operation. During the heat sealingoperation up to 10% or more of the thickness of the heat sealableportion of the multi-layered molded article melts, yet the interiorpolymeric material remains intact and functional as a barrier layer or ascavenger layer in the multi-layered molded article.

In other embodiments, exemplary methods for forming a multi-layer moldedarticle with a heat sealable zone are taught. The exemplary methodsinject the interior layer polymeric material to the side of the zerovelocity gradient of a combined material flow that is opposite or awayfrom the heat-seal surface of a heat-sealable portion of the resultingmulti-layer molded article. The interior layer polymeric material formsa barrier layer or a scavenger layer in the resulting multi-layer moldedarticle. The barrier layer or the scavenger layer is embedded in a skinformed from the inner and outer polymeric material. The exemplarymethods form the resulting multi-layer molded article with a heatsealable portion to which a closure or other component may beheat-sealed. The exemplary methods direct a leading edge of the interiorpolymeric material into the heat sealable portion and subsequentlyposition the leading edge of the interior polymeric material in the heatsealable portion to avoid failure of a heat seal of the resultingmulti-layer article during a heat sealing operation. During the heatsealing operation up to 10% or more of the thickness of the heatsealable portion of the multi-layered molded article melts, yet theinterior polymeric material remains intact and functional as a barrierlayer or a scavenger layer in the multi-layered molded article.

In some embodiments, a co-molded article has an inner layer, an outerlayer and an interior layer substantially contained within the inner andouter layers and heat sealable portion with a surface portion to which aclosure or other component may be heat-sealed. The interior layer may beof a material different than and/or have different compositions from theinner and outer layer. The interior layer may include materials and/orcompositions exhibiting increased gas-impermeability orgas-scavengability relative to the inner and outer layer material. Theinterior layer is positioned in the heat sealable portion in a mannerthat avoids barrier layer failure or scavenger layer failure due to aheat sealing operation. A component (e.g., a lid or a seal) may beheat-sealed to the surface portion of the co-molded article, forming anintact heat-seal between the component and the surface portion. Duringthe heat sealing operation up to 10% or more of the thickness of theheat sealable portion of the multi-layered molded article melts, yet theinterior polymeric material remains intact and functional as a barrierlayer or a scavenger layer in the multi-layered molded article.

In some embodiments, computer readable mediums holding computerexecutable instructions are taught. Execution of the instructions by aprocessor controls formation of a co-molded multi-layer article astaught herein. Execution of the instructions causes injection of aninterior layer polymeric material to the side of the zero velocitygradient of a combined material flow that is opposite or away from aheat-sealable surface portion of a resulting multi-layer molded article.The interior layer polymeric material forms a barrier layer or ascavenger layer in the resulting multi-layer molded article. The barrierlayer or the scavenger layer is embedded in a skin formed from the innerand outer polymeric material. The exemplary instructions when executedform the resulting multi-layer molded article with a heat sealableportion to which a closure or other component may be heat-sealed.Execution of the exemplary instructions direct a leading edge of theinterior polymeric material into the heat sealable portion andsubsequently position the leading edge of the interior polymericmaterial in the heat sealable portion to avoid failure of the innerlayer in the sealable portion during a heat sealing operation. Duringthe heat sealing operation up to 10% or more of the thickness of theheat sealable portion of the multi-layered molded article melts, yet theinterior polymeric material remains intact and functional as a barrierlayer or a scavenger layer in the multi-layered molded article. The heatsealing operation may affix a closure or other component to themulti-layered molded article.

Other objects and advantages of the exemplary embodiments will becomeapparent in view of the following detailed description of theembodiments and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view of a container according toan embodiment of the invention, but with the wall thickness of thecontainer exaggerated for illustrative purposes.

FIG. 2 is schematic cross-sectional view of a mold cavity according toan embodiment of the invention.

FIG. 3 is an enlarged view of the flange portion shown in FIG. 1.

FIG. 4 depicts a cross-sectional view of an exemplary molding systemaccording to various embodiments taught herein.

FIG. 5 illustrates an exemplary computing environment suitable forpracticing exemplary embodiments taught herein.

FIG. 6 is a cross-sectional view of the fountain flow effect of acombined polymeric stream as it flows along an annular pathway of a moldcavity.

FIGS. 7A and 7B are cross-sectional views of the velocity profile of thecombined annular flow of the polymeric stream and the relative velocitydifferences across the flow gradient of the combined polymeric stream.

FIG. 7C is a graph illustrating resulting flow fraction and velocityprofile curves across the annular channel within a nozzle such as inFIG. 4 or for an annular channel in a mold cavity.

DETAILED DESCRIPTION

Disclosed herein are exemplary co-injection molding apparatuses,multi-layer molded articles and containers, and methods to form andcontrol a barrier layer or the scavenger layer in a multi-layer moldingprocess to ensure the integrity of the barrier layer or the scavengerlayer and/or a heat seal zone during and after the implementation of aheat seal process to seal an opening in the multi-layer molded articleor container. By ensuring the integrity of the barrier layer or thescavenger layer and/or the heat seal zone, the container is created suchthat the barrier layer or the scavenger layer and/or the heat seal zoneis fully intact with no breaches or weakened areas, and thus the shelflife of the container is extended. The integrity of the heat seal in theheat seal zone is ensured by restricting the barrier layer or thescavenger layer from contacting a heat sealable surface of the heat sealzone or becoming positioned in an area close to the surface of the heatseal zone through which it may become exposed during the heat sealprocess. This allows a lid or seal to be fully secured to the containerat the heat seal zone. Should the barrier layer or the scavenger layerbreach the heat sealable surface, before, during or after a heat sealprocess then a proper seal would not form between a lid or seal and theheat sealable surface, causing the shelf life of the container todecrease. Likewise, the integrity of the barrier layer or the scavengerlayer is maintained by positioning the barrier layer or the scavengerlayer in the heat seal zone that does not cause the barrier layer or thescavenger layer to melt, breach or perforate during a heat seal process.

Referring to FIG. 1, a container 100 has a bottom 105, a sidewall 110extending from the periphery of the bottom 105 to form a chamber 106,which is generally cup-shaped or U-shaped in this embodiment, having anopen end 107, and a flange 115 extending from the periphery of thesidewall 110 at the open end 107 of the container. A closure 120, whichmay be of the conventional type, may be heat-sealed to the flange 115 byconventional heat sealing methods. The container 100 includes a heatsealable zone 180 with a heat seal surface 182. In this embodiment, theheat sealable zone 180 extends circumferentially about the open end 107.Likewise, in this embodiment the heat seal surface 182 extendscircumferentially about the open end 107. In this embodiment the heatsealable zone 180 and the heat seal surface 182 are formed in the flange115. Though the illustrative embodiment has a cup-like shape, otherexemplary embodiments contemplate containers having any shape orconfiguration in which a heat-seal is used to seal a portion of thecontainer.

The container 100 may be formed by injecting a first plastic material,such as, for example, Ethylene Vinyl Alcohol (EVOH), and a secondplastic material, such as, for example, Polyethylene (PE) orPolypropylene (PP) into a mold cavity configured so as to form an innerlayer 130, an interior layer 150 and an outer layer 132 generallyconforming to the desired end shape of the container or article,accounting for manufacturing requirements (e.g., thermalexpansion/contraction) as is known. Though PE, PP and EVOH are commonlyused materials, it should be understood that other suitable materialsmay be used, and that the invention applies using other materials. Insome embodiments, either PE or PP is used to form the inner and outerlayers of the resulting multi-layer article and EVOH is used to form theinterior layer of the resulting multi-layer article.

As can be seen in FIG. 1, the interior layer 150 extends substantiallythroughout the entirety of the container 100, but is fully surrounded byor embedded between the inner layer 130 and the outer layer 132. Theinterior layer 150 can be a gas barrier material, such as EVOH or othersuitable materials that are known or may become known, that sufficientlyprevents gases, for example, oxygen, from permeating through thecontainer, i.e., from the outside to the inside and vice versa. Theinterior layer 150 can be a gas scavenger material that sufficientlyscavenges gases, for example, oxygen. As can be seen in the particularembodiment of FIG. 1, the interior layer 150 extends into the flange115.

Exemplary embodiments position and cause a leading edge of the polymericmaterial forming the interior layer 150 to fold over or wrap aroundtoward the outer layer 132 within the heat-sealable zone 180. The foldover portion 150 a of the interior layer 150 assures that the interiorlayer 150 will be encapsulated within inner and outer layers, 130 and132 respectively, while extending substantially into the heat-sealablezone, 180, fully around the perimeter of the container. Any gaps wherethe interior layer does not extend into heat-sealable zone may allowexcess gas permeation into the sealed container, which is undesirable asit can shorten the shelf life of the contents held in a resultingcontainer. During a heat sealing operation up to 10% or more of thethickness of the material in the heat-sealable zone 180 melts to form agas impermeable bond between the closure and the container.

Absent the fold over portion 150 a biased toward the outer layer 132during the heat sealing operation, the interior layer 150 at or justbelow the heat-sealable surface 182 may affect the sealing between theclosure and the container because the adhesion between the firstpolymeric material and the closure material may not be as good asbetween the second polymeric material and the closure material. Further,absent the fold over portion 150 a biased toward the outer layer 132 orthe inner layer 130, the interior layer 150 does not extend into thecomplete perimeter of the heat-sealable zone 180 and therefore, part ofthe sealable portion of the container surface is not covered by barriermaterial, thus allowing excessive permeation of O₂ into the containercontents sealed therein. For example, if as little as 1%-2% of the partsurface area does not have interior layer coverage, the shelf life ofthe goods sealed within the container can be shortened due to the highpermeation rate through the outer layer 132. The fold over portion 150 aadvantageously assures that interior layer 150 extends into the completeperimeter of the heat sealable zone 180 and completely around theperimeter of the part.

Beneficially, the interior layer 150 via the fold over portion 150 aextends into the heat sealable zone 180 and is properly distanced fromthe heat sealable surface 182. Consequently, should the interior layer150 be positioned just below the heat sealable surface 182 then theadhesion between the heat seal closure and the container flange isconsidered poor, weak or does not occur. Poor or weak adhesiondetrimentally allows O₂ permeation between the heat seal closure and thecontainer.

Proper positioning of the fold over portion 150 a in or into the heatsealable zone 180 can be advantageously performed in accordance with theteachings herein. Should the interior layer 150 breach the inner layer130 of the container 100 at the heat sealable surface 182 then it islikely that water absorbed by some barrier materials (for example, EVOH)would decrease the barrier property of the material and reduce the shelflife of the container. Further, if the interior layer 150 were to breachthe inner layer 130 of the container 100 at the heat sealable surface182 then it is likely that the interior layer 150 would contact andadhere to the heat sealable surface 182. If this were to occur, the heatseal closure may not fully adhere to the heat sealable surface 182 dueto the contamination caused by the interior layer 150 and reduce theshelf life of the container.

The interior layer 150 may be created by simultaneously injecting afirst polymeric material forming the interior layer 150 with a secondpolymeric material forming the inner layer 130 and the outer layer 132.Such methods are generally known, such as described in U.S. Pat. No.6,908,581 and the documents incorporated therein, also incorporated byreference herein.

As shown schematically in FIG. 2, a mold 200 has mold portions 210 a,210 b that form a mold cavity 220 therebetween. A combined annular flow300 from a nozzle assembly is injected into the mold cavity 220 throughan injection gate at gate injection location 140, and the combinedannular flow 300 flows from the injection location 140 through the moldcavity 220. The combined annular flow 300 is formed in the nozzleassembly. The nozzle assembly forms the combined annular flow 300 fromthe first polymeric material for the interior layer 150 and from thesecond polymeric material for the inner layer 130 and the outer layer132. The second polymeric material forms an inner annular flow and anouter annular flow while the first polymeric material forms an interiorannular flow positioned between the inner annular flow and the outerannular flow of the combined annular flow 300. The flow of the combinedannular flow 300 forms a flow front 330 that moves through the moldcavity 220.

The volumetric flow volume ratio of the inner flow to the outer flowforming the combined annular flow 300 is selected to cause the interiorlayer flow stream to flow along a flow line offset from the zerovelocity gradient 340 (Vmax) of the combined annular flow 300, yet on aflow line having a greater velocity than the average flow velocity(Vave) 360 and biased toward the outer flow. This prevents the interiorlayer material flow 150 from breaking through the flow front 330.Rather, the positioning and the timing of injecting the leading edge ofthe first polymeric material beneficially directs, as shown in FIG. 3,the leading edge of the interior layer material flow 150 to enter theflange 115 and, in turn fold over toward the resulting outer layer 132within the heat-sealable zone 180 to form the fold over portion 150 a.Beneficially, the leading edge of the first polymeric material remainsbehind the flow front 330 and remains encased by the inner and outerflows of the combined annular flow 300. By starting the interior layermaterial flow 150 offset from the zero velocity gradient, or shiftingthe interior layer material flow 150 from the zero velocity gradient toa slower moving flow line biased toward the outer flow of the secondpolymeric material, the first polymeric material has a velocity that isgreater that the average velocity. Thus, the first polymeric material ofthe interior layer can “catch up” to the fountain flow of the combinedflow 130 and fold over, creating a barrier or scavenger layer thatextends into the flange 115 and avoids failure as a barrier or scavengerduring a heat sealing operation to seal the open end 107 of thecontainer 100.

While the techniques of U.S. Pat. No. 6,908,581 prevent the interiorlayer material from breaking through the flow front 330 anddetrimentally flowing onto the heat sealable surface 182, the presentinventor has found that heat-seal failure can still occur due to theleading edge of the first polymeric material detrimentally flowing ontoor close to the heat sealable surface 182. What the inventor hasdiscovered is that by offsetting the flow path of the first polymericmaterial of the interior layer 150 toward the side of the outer layer132 and off of the zero velocity gradient 340, the fold over portion 150a preserves the integrity of the adhesion of the interior layer 150 tothe inner and outer layers and preserves the integrity of the adhesionof the closure to the heat-sealable surface 182 of the second polymericmaterial during and after the heat sealing operation to maintain barriercoverage or scavenger coverage in the container 100.

FIG. 4 illustrates an exemplary system suitable for practicing exemplaryembodiments. Co-injection molding system 1000 is configured to inject atleast two materials into a mold cavity. Materials suitable for use withthe present invention include polymer based materials such as,Polyethylene Terephtholate (PET), Polypropylene (PP), ethylene vinylalcohol (EVOH), and polycarbonates. Co-injection molding system 1000includes a first material source 1200, a second material source 1400,and a manifold 1600. Co-injection molding system 1000 further includesnozzle assemblies 18A-18D and mold 2400. Mold 2400 includes gates20A-20D, and cavities 22A-22D.

A first polymeric material is extruded from the first material source1200 and a second polymeric material is extruded from the secondmaterial source 1400 into the manifold 1600 for combining in nozzles18A-18D before being injected into mold cavities 22A-22D. The first andsecond polymeric streams are combined to form an annular combinedpolymeric stream such that the first polymeric material forms aninterior core stream in the combined polymeric stream while the secondpolymeric material forms the inner and outer streams in the combinedstream. The inner and outer streams encase the interior core stream asthe annular combined polymeric stream is injected from the nozzle.

FIG. 5 illustrates an exemplary computing environment suitable forpracticing exemplary embodiments taught herein. The environment mayinclude a co-injection control device 900 coupled, wired, wirelessly ora hybrid of wired and wirelessly, to co-injection system 1000. Thecon-injection control device 900 is programmable to implement executableBarrier Protection Code 950 for forming a barrier layer or scavengerlayer in a heat sealable portion of a multi-layer molded article thatremains intact during and after the heat sealing operation. Co-injectioncontrol device 900 includes one or more computer-readable media forstoring one or more computer-executable instructions or software forimplementing exemplary embodiments. The computer-readable media mayinclude, but are not limited to, one or more types of hardware memory,non-transitory tangible media, etc. For example, memory 906 included inthe co-injection control device 900 may store computer-executableinstructions or software, e.g., instructions for implementing andprocessing every module of the executable Barrier Protection Code 950.Co-injection control device 900 also includes processor 902 and, one ormore processor(s) 902′ for executing software stored in the memory 906,and other programs for controlling system hardware. Processor 902 andprocessor(s) 902′ each can be a single core processor or multiple core(904 and 904′) processor.

Virtualization may be employed in co-injection control device 900 sothat infrastructure and resources in the computing device can be shareddynamically. Virtualized processors may also be used with the executableBarrier Protection Code 950 and other software in storage 916. A virtualmachine 914 may be provided to handle a process running on multipleprocessors so that the process appears to be using only one computingresource rather than multiple. Multiple virtual machines can also beused with one processor.

Memory 906 may comprise a computer system memory or random accessmemory, such as DRAM, SRAM, EDO RAM, etc. Memory 906 may comprise othertypes of memory as well, or combinations thereof.

A user may interact with co-injection control device 900 through avisual display device 922, such as a computer monitor, which may displaythe user interfaces 924 or any other interface. The visual displaydevice 922 may also display other aspects or elements of exemplaryembodiments, e.g. the databases, SPC historical data, etc. Co-injectioncontrol device 900 may include other I/O devices such a keyboard or amulti-point touch interface 908 and a pointing device 910, for example amouse, for receiving input from a user. The keyboard 908 and thepointing device 910 may be connected to the visual display device 922.Co-injection control device 900 may include other suitable conventionalI/O peripherals. Co-injection control device 900 may further comprise astorage device 916, such as a hard-drive, CD-ROM, or othernon-transitory computer readable media, for storing an operating system918 and other related software, and for storing executable BarrierProtection Code 950.

Co-injection control device 900 may include a network interface 912 tointerface to a Local Area Network (LAN), Wide Area Network (WAN) or theInternet through a variety of connections including, but not limited to,standard telephone lines, LAN or WAN links (e.g., 802.11, T1, T3, 56 kb,X.25), broadband connections (e.g., ISDN, Frame Relay, ATM), wirelessconnections, controller area network (CAN), or some combination of anyor all of the above. The network interface 912 may comprise a built-innetwork adapter, network interface card, PCMCIA network card, card busnetwork adapter, wireless network adapter, USB network adapter, modem orany other device suitable for interfacing authorization computing device900 to any type of network capable of communication and performing theoperations described herein. Moreover, co-injection control device 900may be any computer system such as a workstation, desktop computer,server, laptop, handheld computer or other form of computing ortelecommunications device that is capable of communication and that hassufficient processor power and memory capacity to perform the operationsdescribed herein.

Co-injection control device 900 can be running any operating system suchas any of the versions of the Microsoft® Windows® operating systems, thedifferent releases of the Unix and Linux operating systems, any versionof the MacOS® for Macintosh computers, any embedded operating system,any real-time operating system, any open source operating system, anyproprietary operating system, any operating systems for mobile computingdevices, or any other operating system capable of running on thecomputing device and performing the operations described herein. Theoperating system may be running in native mode or emulated mode.

Barrier Protection Code 950 includes executable code executable by theprocessor 902 to control the co-injection system 1000 to selectivelycontrol a volumetric flow volume of the inner and outer polymericstreams, control a position of the interior core material stream 150relative to a flow front of the combined polymeric stream and controlextrusion start time of the interior core stream relative to theextrusion start time of the inner and outer polymeric streams as taughtherein. That is, Barrier Protection Code 950 includes executable codeexecutable by the processor 902 to control the co-injection system 1000to place or direct a leading edge of the interior core material flowstream 150 on a flow streamline that has a velocity that is greater thatthe average velocity of the combined annular flow 300. The BarrierProtection Code 950 includes executable code executable by the processor902 to control the co-injection system 1000 to place or direct a leadingedge of the interior core material flow stream 150 on a flow streamlinebiased toward the resulting outer layer 132, to place or direct aleading edge of the interior core material flow stream 150 into adownstream heat sealable zone and have the leading edge of the interiorcore material flow stream 150 to fold over in or near the heat sealablezone to avoid a barrier layer or scavenger layer failure during or aftera heat sealing process. The interior core material flow stream 150 foldsover toward the resulting outer wall 132. Execution of the BarrierProtection Code 950 by the processor 902 allows the co-injection system1000 to place the interior layer material flow 150 in a heat sealablezone of the resulting multi-layer plastic article to avoid a breach orfailure of the interior layer 150 in the resulting multi-layer moldedarticle during or after a heat sealing operation. Specifically, theBarrier Protection Code 950 of the present invention aims to ensure theintegrity of the interior layer 150 and ensure the integrity of the heatsealable surface 182 by restricting the interior layer 150 fromcontacting and contaminating the heat sealable surface 182, as discussedpreviously. Methods and co-injection systems taught herein facilitatethe co-injection molding of heat-sealable food or beverage containerswhereby the interior core stream is located in a heat sealable zone tomaintain its integrity during a heat sealing operation.

FIG. 6 depicts the fountain flow effects whereby combined flow has avelocity gradient 22 such that the volumetric flow rate is fastest inthe middle and slowest at or near the interface of the combinedpolymeric stream and the walls of the annular channels of the moldcavity. The flow front of the combined flow 23 shows the fountain floweffect that occurs during polymer flow between cavity walls. Thefountain flow of polymers causes the outer surfaces of a molded part tobe comprised of material that had flowed along the zero-gradient of theflow upstream of the flow front. If the interior layer flows along thezero-gradient of the combined flow, it will “fountain flow” onto theinner or outer surface of the molded part if it reaches the flow frontof the combined polymer flow before the flow front reaches the end ofthe mold cavity.

FIGS. 7A and 7B depicts the velocity gradient, where the combined streamis fastest at point “A” and slower at point “C”. The zero-velocitygradient occurs at the point where the velocity of the flow is greatest.Because the flow at the zero-velocity gradient streamline is greaterthan the average velocity of the flow-front, the interior materialinjected at the zero velocity gradient point can, under somecircumstances “catch up” to and pass the flow-front and break throughthe skin, even if injection of the interior material begins afterinjection of the inner and outer layers (PET or PP). The interior corestream material will breakthrough when the interior material reaches theflow-front of the zero-velocity gradient.

FIG. 7C plots the ratio of flow velocity-to-average flow velocity as afunction of the radius of the annulus between the inner and outer flowchannel walls. FIG. 7C depicts the normalized velocity profile 350 andvolume fraction inside and outside for a fluid with n=0.8 (where n isthe parameter for the non-Newtonian power law model of fluid flow). Thezero gradient 340 for the combined flow stream (CF) is marked on thenormalized velocity profile 350. The curve designated with a circlemarker plots the inner flow (IF) between the radius and the innercylindrical wall T from the inner to the outer wall. The curve markedwith a triangle plots the outer flow (OF) between the outer cylindricalwall and the annular radius. The hatched area shows the acceptablelocation for interior layer placement that is both greater than theaverage velocity and off the zero velocity gradient 340. The interiorlayer material placed within this area will wrap to the outside of thepart. From the graph we can see that the flow fraction of the outsidelayer can be in a range from 0.1 to 0.45. The flow fraction of theinside layer can be from 0.9 to 0.55. The interior layer thickness canbe as thick as about 25% of the thickness of the flowing layer which isabout 35% of the flow fraction, 0.1 to 0.45. If the hatched area were onthe opposite side of the zero velocity gradient 340, the flow fractionof the inside layer and outside layer would be of similar magnitude, butinversed, and the interior layer would then wrap toward the inside wall.

Exemplary embodiments have the foldover biased away from theheat-sealable surface when the adhesion between the closure and thecontainer flange may be affected by the adhesion of the interior layermaterial, the inner layer material and/or the closure material to eachother. Other embodiments may have the interior layer biased toward theheat-sealable zone when closure adhesion is not adversely affected bythe proximity of the interior layer to the heat-sealable surface.

As may be recognized by those of ordinary skill in the pertinent artbased on the teachings herein, numerous changes and modifications may bemade to the above-described and other embodiments of the presentdisclosure without departing from the spirit of the invention as definedin the appended claims. Accordingly, this detailed description ofembodiments is to be taken in an illustrative, as opposed to a limiting,sense.

What is claimed is:
 1. A co-injection molding apparatus comprising amold defining a mold cavity, the molding apparatus comprising: a nozzleassembly configured to inject a first polymeric material into a moldcavity configured to form an interior layer of a resulting multi-layerarticle and to inject a second polymeric material into the mold cavityto form an inner layer and an outer layer of the resulting multi-layerarticle; and a processor programmed to execute instructions to positiona flow of the first polymeric material in a heat sealable zone of theresulting multi-layer article to avoid a failure in the resultingmulti-layer article when the heat sealable zone melts during a heatsealing operation by co-injecting the first polymeric material into themold cavity along a flow line offset from a zero-velocity gradient of acombined flow of the first and second polymeric materials, and whereinthe processor is further programmed to execute instructions to cause thefirst polymeric material to fold over in the heat sealable zone awayfrom a heat seal contact surface.
 2. A co-injection molding apparatus asdefined in claim 1, wherein the failure is a breach in the integrity ofthe layers of the resulting multi-layer article.
 3. A co-injectionmolding apparatus as defined in claim 2, wherein the breach in theintegrity of the layers damages the performance of the resultingmulti-layer article.
 4. A co-injection molding apparatus as defined inclaim 1, wherein the failure is a breach in the integrity of a heatsealable portion of the resulting multi-layer article.
 5. A co-injectionmolding apparatus as defined in claim 1, wherein the processor isfurther programmed to execute instructions to maintain the flow line ofthe first polymeric material offset from the zero-velocity gradient ofthe combined flow throughout co-injection of the first polymericmaterial into the mold cavity.
 6. A co-injection molding apparatus asdefined in claim 1, wherein the processor is further programmed toexecute instructions to co-inject the first polymeric material along aflow line biased toward a resulting outer wall surface of the resultingmulti-laver article.
 7. A co-injection molding apparatus as defined inclaim 1, wherein the processor is further programmed to executeinstructions to maintain the flow line of the first polymeric materialalong a flow line biased toward a resulting outer wall surface of theresulting multi-layer article.
 8. A co-injection molding apparatus asdefined in claim 7, wherein the flow line offset is selected based on alocation of a heat sealable surface in the heat sealable zone of theresulting multi-layer article.
 9. A co-injection molding apparatus asdefined in claim 1, wherein the resulting multi-layer article includesan open end opposed to a closed end, and a flange disposed at the openend with the flange including the heat sealable zone.
 10. A co-injectionmolding apparatus as defined in claim 1, wherein the heat sealable zoneof the resulting multi-layer article includes a sealable surfacesubstantially parallel to an orientation of the interior layer of thefirst polymeric material in the heat sealable zone of the resultingmulti-layer article.